/*
 * Copyright 2002-2015 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package qunar.tc.bistoury.instrument.client.spring.el;


import org.objectweb.asm.MethodVisitor;

import java.math.BigDecimal;
import java.math.BigInteger;

/**
 * The minus operator supports:
 * <ul>
 * <li>subtraction of numbers
 * <li>subtraction of an int from a string of one character
 * (effectively decreasing that character), so 'd'-3='a'
 * </ul>
 *
 * <p>It can be used as a unary operator for numbers.
 * The standard promotions are performed when the operand types vary (double-int=double).
 * For other options it defers to the registered overloader.
 *
 * @author Andy Clement
 * @author Juergen Hoeller
 * @author Giovanni Dall'Oglio Risso
 * @since 3.0
 */
class OpMinus extends Operator {

    public OpMinus(int pos, SpelNodeImpl... operands) {
        super("-", pos, operands);
    }


    @Override
    public TypedValue getValueInternal(ExpressionState state) throws EvaluationException {
        SpelNodeImpl leftOp = getLeftOperand();
        SpelNodeImpl rightOp = getRightOperand();

        if (rightOp == null) {  // if only one operand, then this is unary minus
            Object operand = leftOp.getValueInternal(state).getValue();
            if (operand instanceof Number) {
                if (operand instanceof BigDecimal) {
                    return new TypedValue(((BigDecimal) operand).negate());
                } else if (operand instanceof Double) {
                    this.exitTypeDescriptor = "D";
                    return new TypedValue(0 - ((Number) operand).doubleValue());
                } else if (operand instanceof Float) {
                    this.exitTypeDescriptor = "F";
                    return new TypedValue(0 - ((Number) operand).floatValue());
                } else if (operand instanceof BigInteger) {
                    return new TypedValue(((BigInteger) operand).negate());
                } else if (operand instanceof Long) {
                    this.exitTypeDescriptor = "J";
                    return new TypedValue(0 - ((Number) operand).longValue());
                } else if (operand instanceof Integer) {
                    this.exitTypeDescriptor = "I";
                    return new TypedValue(0 - ((Number) operand).intValue());
                } else if (operand instanceof Short) {
                    return new TypedValue(0 - ((Number) operand).shortValue());
                } else if (operand instanceof Byte) {
                    return new TypedValue(0 - ((Number) operand).byteValue());
                } else {
                    // Unknown Number subtypes -> best guess is double subtraction
                    return new TypedValue(0 - ((Number) operand).doubleValue());
                }
            }
            return state.operate(Operation.SUBTRACT, operand, null);
        }

        Object left = leftOp.getValueInternal(state).getValue();
        Object right = rightOp.getValueInternal(state).getValue();

        if (left instanceof Number && right instanceof Number) {
            Number leftNumber = (Number) left;
            Number rightNumber = (Number) right;

            if (leftNumber instanceof BigDecimal || rightNumber instanceof BigDecimal) {
                BigDecimal leftBigDecimal = NumberUtils.convertNumberToTargetClass(leftNumber, BigDecimal.class);
                BigDecimal rightBigDecimal = NumberUtils.convertNumberToTargetClass(rightNumber, BigDecimal.class);
                return new TypedValue(leftBigDecimal.subtract(rightBigDecimal));
            } else if (leftNumber instanceof Double || rightNumber instanceof Double) {
                this.exitTypeDescriptor = "D";
                return new TypedValue(leftNumber.doubleValue() - rightNumber.doubleValue());
            } else if (leftNumber instanceof Float || rightNumber instanceof Float) {
                this.exitTypeDescriptor = "F";
                return new TypedValue(leftNumber.floatValue() - rightNumber.floatValue());
            } else if (leftNumber instanceof BigInteger || rightNumber instanceof BigInteger) {
                BigInteger leftBigInteger = NumberUtils.convertNumberToTargetClass(leftNumber, BigInteger.class);
                BigInteger rightBigInteger = NumberUtils.convertNumberToTargetClass(rightNumber, BigInteger.class);
                return new TypedValue(leftBigInteger.subtract(rightBigInteger));
            } else if (leftNumber instanceof Long || rightNumber instanceof Long) {
                this.exitTypeDescriptor = "J";
                return new TypedValue(leftNumber.longValue() - rightNumber.longValue());
            } else if (CodeFlow.isIntegerForNumericOp(leftNumber) || CodeFlow.isIntegerForNumericOp(rightNumber)) {
                this.exitTypeDescriptor = "I";
                return new TypedValue(leftNumber.intValue() - rightNumber.intValue());
            } else {
                // Unknown Number subtypes -> best guess is double subtraction
                return new TypedValue(leftNumber.doubleValue() - rightNumber.doubleValue());
            }
        }

        if (left instanceof String && right instanceof Integer && ((String) left).length() == 1) {
            String theString = (String) left;
            Integer theInteger = (Integer) right;
            // Implements character - int (ie. b - 1 = a)
            return new TypedValue(Character.toString((char) (theString.charAt(0) - theInteger)));
        }

        return state.operate(Operation.SUBTRACT, left, right);
    }

    @Override
    public String toStringAST() {
        if (getRightOperand() == null) {  // unary minus
            return "-" + getLeftOperand().toStringAST();
        }
        return super.toStringAST();
    }

    @Override
    public SpelNodeImpl getRightOperand() {
        if (this.children.length < 2) {
            return null;
        }
        return this.children[1];
    }

    @Override
    public boolean isCompilable() {
        if (!getLeftOperand().isCompilable()) {
            return false;
        }
        if (this.children.length > 1) {
            if (!getRightOperand().isCompilable()) {
                return false;
            }
        }
        return (this.exitTypeDescriptor != null);
    }

    @Override
    public void generateCode(MethodVisitor mv, CodeFlow cf) {
        getLeftOperand().generateCode(mv, cf);
        String leftDesc = getLeftOperand().exitTypeDescriptor;
        CodeFlow.insertNumericUnboxOrPrimitiveTypeCoercion(mv, leftDesc, this.exitTypeDescriptor.charAt(0));
        if (this.children.length > 1) {
            cf.enterCompilationScope();
            getRightOperand().generateCode(mv, cf);
            String rightDesc = getRightOperand().exitTypeDescriptor;
            cf.exitCompilationScope();
            CodeFlow.insertNumericUnboxOrPrimitiveTypeCoercion(mv, rightDesc, this.exitTypeDescriptor.charAt(0));
            switch (this.exitTypeDescriptor.charAt(0)) {
                case 'I':
                    mv.visitInsn(ISUB);
                    break;
                case 'J':
                    mv.visitInsn(LSUB);
                    break;
                case 'F':
                    mv.visitInsn(FSUB);
                    break;
                case 'D':
                    mv.visitInsn(DSUB);
                    break;
                default:
                    throw new IllegalStateException(
                            "Unrecognized exit type descriptor: '" + this.exitTypeDescriptor + "'");
            }
        } else {
            switch (this.exitTypeDescriptor.charAt(0)) {
                case 'I':
                    mv.visitInsn(INEG);
                    break;
                case 'J':
                    mv.visitInsn(LNEG);
                    break;
                case 'F':
                    mv.visitInsn(FNEG);
                    break;
                case 'D':
                    mv.visitInsn(DNEG);
                    break;
                default:
                    throw new IllegalStateException(
                            "Unrecognized exit type descriptor: '" + this.exitTypeDescriptor + "'");
            }
        }
        cf.pushDescriptor(this.exitTypeDescriptor);
    }

}
